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# Copyright (c) 2010 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""GDB support for WebKit types.
Add this to your gdb by amending your ~/.gdbinit as follows:
python
import sys
sys.path.insert(0, "/path/to/tools/gdb/")
import webkit
"""
import gdb
import struct
def ustring_to_string(ptr, length=None):
"""Convert a pointer to UTF-16 data into a Python Unicode string.
ptr and length are both gdb.Value objects.
If length is unspecified, will guess at the length."""
extra = ''
if length is None:
# Try to guess at the length.
for i in xrange(0, 2048):
if int((ptr + i).dereference()) == 0:
length = i
break
if length is None:
length = 256
extra = u' (no trailing NUL found)'
else:
length = int(length)
char_vals = [int((ptr + i).dereference()) for i in xrange(length)]
string = struct.pack('H' * length, *char_vals).decode('utf-16', 'replace')
return string + extra
class StringPrinter(object):
"Shared code between different string-printing classes"
def __init__(self, val):
self.val = val
def display_hint(self):
return 'string'
class UCharStringPrinter(StringPrinter):
"Print a UChar*; we must guess at the length"
def to_string(self):
return ustring_to_string(self.val)
class WebCoreAtomicStringPrinter(StringPrinter):
"Print a WebCore::AtomicString"
def to_string(self):
return self.val['m_string']
class WebCoreStringPrinter(StringPrinter):
"Print a WebCore::String"
def get_length(self):
if not self.val['m_impl']['m_ptr']:
return 0
return self.val['m_impl']['m_ptr']['m_length']
def to_string(self):
if self.get_length() == 0:
return '(null)'
return ustring_to_string(self.val['m_impl']['m_ptr']['m_data'],
self.get_length())
class WebCoreQualifiedNamePrinter(StringPrinter):
"Print a WebCore::QualifiedName"
def __init__(self, val):
super(WebCoreQualifiedNamePrinter, self).__init__(val)
self.prefix_length = 0
self.length = 0
if self.val['m_impl']:
self.prefix_printer = WebCoreStringPrinter(
self.val['m_impl']['m_prefix']['m_string'])
self.local_name_printer = WebCoreStringPrinter(
self.val['m_impl']['m_localName']['m_string'])
self.prefix_length = self.prefix_printer.get_length()
if self.prefix_length > 0:
self.length = (self.prefix_length + 1 +
self.local_name_printer.get_length())
else:
self.length = self.local_name_printer.get_length()
def get_length(self):
return self.length
def to_string(self):
if self.get_length() == 0:
return "(null)"
else:
if self.prefix_length > 0:
return (self.prefix_printer.to_string() + ":" +
self.local_name_printer.to_string())
else:
return self.local_name_printer.to_string()
def lookup_function(val):
"""Function used to load pretty printers; will be passed to GDB."""
lookup_tag = val.type.tag
printers = {
"WebCore::AtomicString": WebCoreAtomicStringPrinter,
"WebCore::String": WebCoreStringPrinter,
"WebCore::QualifiedName": WebCoreQualifiedNamePrinter,
}
name = val.type.tag
if name in printers:
return printers[name](val)
if val.type.code == gdb.TYPE_CODE_PTR:
name = str(val.type.target().unqualified())
if name == 'UChar':
return UCharStringPrinter(val)
return None
gdb.pretty_printers.append(lookup_function)
class PrintPathToRootCommand(gdb.Command):
"""Command for printing WebKit Node trees.
Usage: printpathtoroot variable_name
"""
def __init__(self):
super(PrintPathToRootCommand, self).__init__("printpathtoroot",
gdb.COMMAND_SUPPORT,
gdb.COMPLETE_NONE)
def invoke(self, arg, from_tty):
element_type = gdb.lookup_type('WebCore::Element')
node_type = gdb.lookup_type('WebCore::Node')
frame = gdb.selected_frame()
try:
val = gdb.Frame.read_var(frame, arg)
except:
print "No such variable, or invalid type"
return
target_type = str(val.type.target().strip_typedefs())
if target_type == str(node_type):
stack = []
while val:
stack.append([val,
val.cast(element_type.pointer()).dereference()['m_tagName']])
val = val.dereference()['m_parent']
padding = ''
while len(stack) > 0:
pair = stack.pop()
print padding, pair[1], pair[0]
padding = padding + ' '
else:
print 'Sorry: I don\'t know how to deal with %s yet.' % target_type
PrintPathToRootCommand()
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